successive generations having passed nearly their whole lives in canoes,
with their lower extremities motionless. Other writers have come to a
similar conclusion in analogous cases. According to Cranz (24. 'History
of Greenland,' Eng. translat., 1767, vol. i. p. 230.), who lived for a long
time with the Esquimaux, "the natives believe that ingenuity and dexterity
in seal-catching (their highest art and virtue) is hereditary; there is
really something in it, for the son of a celebrated seal-catcher will
distinguish himself, though he lost his father in childhood." But in this
case it is mental aptitude, quite as much as bodily structure, which
appears to be inherited. It is asserted that the hands of English
labourers are at birth larger than those of the gentry. (25.
'Intermarriage,' by Alex. Walker, 1838, p. 377.) From the correlation
which exists, at least in some cases (26. 'The Variation of Animals under
Domestication,' vol. i. p. 173.), between the development of the
extremities and of the jaws, it is possible that in those classes which do
not labour much with their hands and feet, the jaws would be reduced in
size from this cause. That they are generally smaller in refined and
civilised men than in hard-working men or savages, is certain. But with
savages, as Mr. Herbert Spencer (27. 'Principles of Biology,' vol. i. p.
455.) has remarked, the greater use of the jaws in chewing coarse, uncooked
food, would act in a direct manner on the masticatory muscles, and on the
bones to which they are attached. In infants, long before birth, the skin
on the soles of the feet is thicker than on any other part of the body;
(28. Paget, 'Lectures on Surgical Pathology,' vol. ii, 1853, p. 209.) and
it can hardly be doubted that this is due to the inherited effects of
pressure during a long series of generations.

It is familiar to every one that watchmakers and engravers are liable to be
short-sighted, whilst men living much out of doors, and especially savages,
are generally long-sighted. (29. It is a singular and unexpected fact